"""
Core functions and attributes for the matplotlib style library:

``use``
    Select style sheet to override the current matplotlib settings.
``context``
    Context manager to use a style sheet temporarily.
``available``
    List available style sheets.
``library``
    A dictionary of style names and matplotlib settings.
"""

import contextlib
import logging
import os
from pathlib import Path
import re
import warnings

import matplotlib as mpl
from matplotlib import cbook, rc_params_from_file, rcParamsDefault

_log = logging.getLogger(__name__)

__all__ = ['use', 'context', 'available', 'library', 'reload_library']


BASE_LIBRARY_PATH = os.path.join(mpl.get_data_path(), 'stylelib')
# Users may want multiple library paths, so store a list of paths.
USER_LIBRARY_PATHS = [os.path.join(mpl.get_configdir(), 'stylelib')]
STYLE_EXTENSION = 'mplstyle'
STYLE_FILE_PATTERN = re.compile(r'([\S]+).%s$' % STYLE_EXTENSION)


# A list of rcParams that should not be applied from styles
STYLE_BLACKLIST = {
    'interactive', 'backend', 'backend.qt4', 'webagg.port', 'webagg.address',
    'webagg.port_retries', 'webagg.open_in_browser', 'backend_fallback',
    'toolbar', 'timezone', 'datapath', 'figure.max_open_warning',
    'figure.raise_window', 'savefig.directory', 'tk.window_focus',
    'docstring.hardcopy', 'date.epoch'}


def _remove_blacklisted_style_params(d, warn=True):
    o = {}
    for key in d:  # prevent triggering RcParams.__getitem__('backend')
        if key in STYLE_BLACKLIST:
            if warn:
                cbook._warn_external(
                    "Style includes a parameter, '{0}', that is not related "
                    "to style.  Ignoring".format(key))
        else:
            o[key] = d[key]
    return o


@cbook.deprecated("3.2")
def is_style_file(filename):
    """Return True if the filename looks like a style file."""
    return STYLE_FILE_PATTERN.match(filename) is not None


def _apply_style(d, warn=True):
    mpl.rcParams.update(_remove_blacklisted_style_params(d, warn=warn))


def use(style):
    """
    Use Matplotlib style settings from a style specification.

    The style name of 'default' is reserved for reverting back to
    the default style settings.

    .. note::

       This updates the `.rcParams` with the settings from the style.
       `.rcParams` not defined in the style are kept.

    Parameters
    ----------
    style : str, dict, Path or list
        A style specification. Valid options are:

        +------+-------------------------------------------------------------+
        | str  | The name of a style or a path/URL to a style file. For a    |
        |      | list of available style names, see `style.available`.       |
        +------+-------------------------------------------------------------+
        | dict | Dictionary with valid key/value pairs for                   |
        |      | `matplotlib.rcParams`.                                      |
        +------+-------------------------------------------------------------+
        | Path | A path-like object which is a path to a style file.         |
        +------+-------------------------------------------------------------+
        | list | A list of style specifiers (str, Path or dict) applied from |
        |      | first to last in the list.                                  |
        +------+-------------------------------------------------------------+

    """
    style_alias = {'mpl20': 'default',
                   'mpl15': 'classic'}
    if isinstance(style, (str, Path)) or hasattr(style, 'keys'):
        # If name is a single str, Path or dict, make it a single element list.
        styles = [style]
    else:
        styles = style

    styles = (style_alias.get(s, s) if isinstance(s, str) else s
              for s in styles)
    for style in styles:
        if not isinstance(style, (str, Path)):
            _apply_style(style)
        elif style == 'default':
            # Deprecation warnings were already handled when creating
            # rcParamsDefault, no need to reemit them here.
            with cbook._suppress_matplotlib_deprecation_warning():
                _apply_style(rcParamsDefault, warn=False)
        elif style in library:
            _apply_style(library[style])
        else:
            try:
                rc = rc_params_from_file(style, use_default_template=False)
                _apply_style(rc)
            except IOError as err:
                raise IOError(
                    "{!r} not found in the style library and input is not a "
                    "valid URL or path; see `style.available` for list of "
                    "available styles".format(style)) from err


@contextlib.contextmanager
def context(style, after_reset=False):
    """
    Context manager for using style settings temporarily.

    Parameters
    ----------
    style : str, dict, Path or list
        A style specification. Valid options are:

        +------+-------------------------------------------------------------+
        | str  | The name of a style or a path/URL to a style file. For a    |
        |      | list of available style names, see `style.available`.       |
        +------+-------------------------------------------------------------+
        | dict | Dictionary with valid key/value pairs for                   |
        |      | `matplotlib.rcParams`.                                      |
        +------+-------------------------------------------------------------+
        | Path | A path-like object which is a path to a style file.         |
        +------+-------------------------------------------------------------+
        | list | A list of style specifiers (str, Path or dict) applied from |
        |      | first to last in the list.                                  |
        +------+-------------------------------------------------------------+

    after_reset : bool
        If True, apply style after resetting settings to their defaults;
        otherwise, apply style on top of the current settings.
    """
    with mpl.rc_context():
        if after_reset:
            mpl.rcdefaults()
        use(style)
        yield


def load_base_library():
    """Load style library defined in this package."""
    library = read_style_directory(BASE_LIBRARY_PATH)
    return library


def iter_user_libraries():
    for stylelib_path in USER_LIBRARY_PATHS:
        stylelib_path = os.path.expanduser(stylelib_path)
        if os.path.exists(stylelib_path) and os.path.isdir(stylelib_path):
            yield stylelib_path


def update_user_library(library):
    """Update style library with user-defined rc files."""
    for stylelib_path in iter_user_libraries():
        styles = read_style_directory(stylelib_path)
        update_nested_dict(library, styles)
    return library


@cbook.deprecated("3.2")
def iter_style_files(style_dir):
    """Yield file path and name of styles in the given directory."""
    for path in os.listdir(style_dir):
        filename = os.path.basename(path)
        if is_style_file(filename):
            match = STYLE_FILE_PATTERN.match(filename)
            path = os.path.abspath(os.path.join(style_dir, path))
            yield path, match.group(1)


def read_style_directory(style_dir):
    """Return dictionary of styles defined in *style_dir*."""
    styles = dict()
    for path in Path(style_dir).glob(f"*.{STYLE_EXTENSION}"):
        with warnings.catch_warnings(record=True) as warns:
            styles[path.stem] = rc_params_from_file(
                path, use_default_template=False)
        for w in warns:
            _log.warning('In %s: %s', path, w.message)
    return styles


def update_nested_dict(main_dict, new_dict):
    """
    Update nested dict (only level of nesting) with new values.

    Unlike `dict.update`, this assumes that the values of the parent dict are
    dicts (or dict-like), so you shouldn't replace the nested dict if it
    already exists. Instead you should update the sub-dict.
    """
    # update named styles specified by user
    for name, rc_dict in new_dict.items():
        main_dict.setdefault(name, {}).update(rc_dict)
    return main_dict


# Load style library
# ==================
_base_library = load_base_library()

library = None

available = []


def reload_library():
    """Reload the style library."""
    global library
    library = update_user_library(_base_library)
    available[:] = sorted(library.keys())


reload_library()
